﻿//Copyright (C) 2011 by Markus Minichmayr

//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:

//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.

//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Minichmayr.Async
{
    /// <summary>
    /// Maps keys to <see cref="IAsyncEnumerable{T}"/> asynchronous sequences.
    /// </summary>
    /// <typeparam name="TKey">The type of the keys.</typeparam>
    /// <typeparam name="TElement">The type of elements in the <see cref="IAsyncEnumerable{T}"/>.</typeparam>
    public interface IAsyncLookup<TKey, TElement> : IAsyncEnumerable<IAsyncGrouping<TKey, TElement>>
    {
        /// <summary>
        /// Asynchronously determines whether an item with the specified key exists in this object.
        /// </summary>
        /// <param name="key">The key to search for.</param>
        /// <returns>A <see cref="Task"/> object that evaluates to <c>true</c> if this instance contains an item with the specified key, or <c>false</c> otherwise.</returns>
        Task<bool> ContainsAsync(TKey key);

        /// <summary>
        /// Asynchronously gets the <see cref="IAsyncEnumerable{T}"/> sequence of values indexed by a specified key.
        /// </summary>
        /// <param name="key">The key to search for.</param>
        /// <returns>A task that evaluates to the <see cref="IAsyncEnumerable{T}"/> indexed by the specified key.</returns>
        Task<IAsyncEnumerable<TElement>> GetAsync(TKey key);
    }
}
